function Stack() {
    this.item = []
}
Stack.prototype.push = function (e) {
    this.item.push(e)
}
Stack.prototype.pop = function () {
    this.item.pop()
}
Stack.prototype.isEmpty = function () {
    return this.item.length === 0 ? true : false
}
Stack.prototype.peek = function () {
    return this.item.shift()
}

module.exports={Stack}